Array system controls request based on information received from host computer

ABSTRACT

For using a plurality of files contained in one logical device with a plurality of processing systems, sharing of a data storage unit among the plurality of processing systems is realized without need for a host processing system to check use states of the files in a server storage unit. Information concerning extent (extent range) of an input/output processing request issued by a host processor is stored in a control memory incorporated in a control unit for allowing the control unit to make decision as to overlap of the extents of the input/output processings to thereby effectuate exclusive control on an extent-by-extent basis.

This application is a continuation of Ser. No. 10/403,277 filed Apr. 1,2003 now U.S. Pat. No. 6,721,823 which is a continuation of Ser. No.09/458,705 filed Dec. 13, 1999 now U.S. Pat. No. 6,567,865.

BACKGROUND OF THE INVENTION

The present invention relates to a data storage system coupled orconnected to a plurality of host processors. More particularly, theinvention is concerned with a technology which can effectively beadopted for enhancing efficiency of exclusive control for the processingof stored data.

In general, there exist a plurality of files in one volume set up in amagnetic disk drive or device. When a file in a given volume is beingused by a given host processor, the volume containing that file assumesa device busy state. As a result of this, access of other host processorto the other file contained in the given volume is forced to wait forreleasing of the volume from the device busy state. This is because suchexclusive use is effectuated that when one host processor is using onevolume, any other host processor is disabled to use that volume.

With the access control scheme mentioned above, there arises a problemthat when a plurality of files exist on a given volume, files other thanthat for which the exclusion is to be effectuated are unnecessarilysubjected to the exclusion, which leads to degradation of fileutilization efficiency. For solving the problem mentioned above, therehas been proposed such approach that a control memory is provided in amagnetic disk control unit for storing information indicating on afile-by-file basis whether or not individual files are being used,wherein the use statuses of the files are checked by a host processorsystem by reading the above-mentioned information from the correspondingcontrol memory, as disclosed, for example, in JP-B-1-15899. In the fileaccess control scheme disclosed in JP-B-1-15899, the exclusive controlis performed on a logical-file basis. Consequently, when sharing of asame file is desired, e.g. when a same file is to be shared by two hostprocessors only for read operation, such sharing of the same file isimpossible because of the exclusion on a file-by-file basis.

Further, JP-A-7-200179 discloses a scheme according to which a physicalvolume is partitioned into a plurality of subvolumes. With the volumemanagement scheme disclosed in JP-A-7-200179, the exclusive control canbe carried out on a subvolume basis. In that case, the subvolume itselfhas to be created upon formatting of the disk. Further, the exclusivecontrol of the subvolumes is performed by the host processor byconfirming or checking the use status of the subvolumes on the basis ofinformation held by an external storage.

In the conventional systems described above, for effectuating theexclusive control on the basis of files contained in a physical volumeor on a subvolume basis, it becomes necessary that the host processingsystem reads from the magnetic disk device the information indicatingwhether or not the files or subvolumes are being used, to thereby checkwhether the file or subvolume of concern is being used or not, which inturn means that the host processing has to be imparted with an especialfunction for the exclusive control. For realizing such exclusivecontrol, alteration or modification of both host software and the serverstorage control unit becomes necessary.

SUMMARY OF THE INVENTION

In the light of the state of the art described above, it is an object ofthe present invention to provide a storage system which is capable ofperforming exclusive control of input/output processing requests on thebasis of files (i.e., on a file-by-file basis) which are contained in avolume in the case where individual files contained in the volume are tobe shared by a plurality of systems, without need for imparting to thehost processing system and/or host software the function for checkingwhether the file or files stored in a server storage unit is being usedor not.

In view of the above and other objects which will become apparent as thedescription proceeds, there is provided according to an aspect of thepresent invention a storage system which is comprised of a control unitincorporating a control memory, wherein information concerning theextent (range) of an input/output processing request (hereinafter alsoreferred to as the input/output processing request extent) which istransferred from a given one of plural host processors to the controlunit upon issuance of the input/output processing request from theformer is stored in the control memory with a view to realizing theexclusive control for a plurality of input/output processing requestsissued from a plurality of host processors to one logical device bymaking use of the extent information mentioned above. When aninput/output processing request is newly issued, decision is made as towhether or not any input/output processing request whose extent overlapswith that of the newly issued input/output processing request is beingexecuted. Unless overlap of the extents is found, the input/outputprocessing as requested currently is executed continuously. On the otherhand, when the extent overlap is found, the newly issued input/outputprocessing request is stored in the control memory as the input/outputprocessing request waiting for execution.

In the control memory incorporated in the control unit, identifiersdefined inherently to the individual input/output processings(hereinafter referred to as the input/output processing requestidentifiers), respectively, and identifiers of paths by way of which theinput/output processing requests are transferred to the control unit(hereinafter also referred to as the path identifiers) are stored on arequest-by-request basis. The extent information of the individualinput/output processing requests is stored in correspondence to theinput/output processing request identifiers, respectively. Further, forthe input/output processing request for which overlap of the extent isdecided and which is thus forced to wait for execution, the informationindicating occurrence of wait-event is stored in correspondence to therelevant input/output processing request identifier.

Furthermore, in the storage system according to the present invention,the wait-event occurrence information stored in the control memory isreferred upon completion of the input/output processing for thepreceding request. When the input/output request waiting for executionin succession to the preceding input/output processing request exists, arequest for reconnection of the input/output processing awaiting theexecution is issued to the host processor.

Besides, in a preferred mode for carrying out the present invention,service equipment having a function for transmitting information to thecontrol memory incorporated in the control unit may be employed forallowing the control unit to inhibit the logical device from theaforementioned exclusive control on the extent-by-extent basis when itis indicated by the service equipment that the extent exclusive controlon the logical-device basis is not to be performed.

The above and other objects, features and attendant advantages of thepresent invention will more easily be understood by reading thefollowing description of the preferred embodiments thereof taken, onlyby way of example, in conjunction with the accompanying drawings, beingappreciated that many modifications and variations of the presentinvention are possible in the light of the teachings disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of the description which follows, reference is made to thedrawings, in which:

FIG. 1 is a block diagram showing schematically a general arrangement ofa storage system according to an embodiment of the present invention;

FIG. 2 is a view for illustrating, by way of example, commandstransferred between host processors and a control unit;

FIG. 3 is a view illustrating a structure of logical device controltables stored in control memories of a control unit in the storagesystem according to an embodiment of the present invention;

FIG. 4 is a view illustrating a structure of input/output processingcontrol tables stored in the control memories of the control unit;

FIG. 5 is a view illustrating a structure of a path group identifiertable stored in the control memories of the control unit;

FIG. 6 is a view illustrating a structure of an extent-basedexclusive-use suppression control table stored in the control memoriesof the control unit;

FIG. 7 is a flow chart for illustrating a processing procedure executedaccording to the teachings of the invention in case an input/outputprocessing request containing extent information is issued;

FIG. 8 is a flow chart for illustrating a processing procedure forexecuting an extent-based exclusive control according to the presentinvention; and

FIG. 9 is a flow chart for illustrating a process for restarting aninput/output processing request forced to wait for execution by theexclusive control according to the present invention.

DESCRIPTION OF THE EMBODIMENTS

The present invention will be described in detail in conjunction withwhat is presently considered as preferred or typical embodiments thereofby reference to the drawings. In the following description, likereference characters designate like or corresponding parts throughoutthe several views.

(A) General Arrangement of Storage System

Referring to FIG. 1, the storage system according to an embodiment ofthe present invention includes a plurality of host processors (#1, #2)10 for performing arithmetic operations or the like by processinginformation or data, channels 11 for performing input/output controlsuch as control of data transfer, an array-type external storage unit14, and a control unit 12 which is in charge of controlling thecomponents or units mentioned above. The storage system now underconsideration is so arranged that read/write data operation for alogical device 143 set up in the array-type external storage unit 14 iscarried out in response to a command issued by a given one of the hostprocessors 10 by way of the relevant channel 11 and a relevant hostadaptor 122, a cache memory 121 and a disk adaptor 123 which areincorporated in the control unit 12.

The control unit 12 incorporates therein control memories 124 which areadapted to store control information used for carrying out controlsdescribed hereinafter and is provided with service equipment 13 whichserves for a function for transmitting external commands to the controlmemory 124. Each of the host adaptors 122 incorporated in the controlunit 12 is designed to control the data transfer with the channels 11.On the other hand, each of the disk adaptors 123 also incorporated inthe control unit 12 is designed to control the read/write data operationfor the logical device or devices 143 set up over a plurality ofphysical devices 142 provided in the array-type external storage unit14. The host adaptor 122 and the disk adaptor 123 perform read/writedata operation for the cache memory 121. Thus, data transfer between thehost adaptor 122 and the disk adaptor 123 can be realized through themedium of the cache memory 121. In the control memory 124, there isstored control information in the form of logical device control tables30, input/output processing control tables 40, a path group identifiertable 50 and an extent-based exclusive-use suppression control table 60,etc., which will be described in detail hereinafter. The host adaptors122, the cache memories 121, the control memories 124 and the diskadaptors 123 are connected or coupled to buses 125, respectively, as canbe seen in FIG. 1.

Now, description will be directed to operation in general of the systemimplemented in the configuration described above. In the read dataoperation, a read request issued from a given one of the host processors10 is first received by the relevant host adaptor 122, whereupon thehost adaptor 122 checks the cache memory 121 as to whether or not thedata as required is available in the cache memory 121. In case therequired data exists in the cache memory, the host adaptor 122 transfersthe data to the relevant host processor 10 from the cache memory. On theother hand, unless the required data is available from the cache memory121, the host adaptor 122 requests the disk adaptor 123 for reading therequired data from the logical device 143 installed internally of thearray-type external storage unit 14. After the disk adaptor 123 hasstored once the required data in the cache memory 121, the host adaptor122 transfers the required data to the host processor 10.

In the write data operation, a write request issued by a given one ofthe host processors 10 is received by the host adaptor 122 incorporatedin the control unit 12. Subsequently, the host adaptor 122 writes thereceived data in the cache memory 121 and sends a write command endmessage indicating completion of the write request to the host processor10. The disk adaptor 123 transfers the data stored temporarily in thecache memory to the logical device 143 to be written at a locationindicated by the write request.

The array-type external storage unit 14 is constituted by a plurality ofarray groups 141, wherein each of the array groups is constituted by aplurality of physical devices 142. The logical devices 143 accessed bythe host processor on a device-by-device basis are set up across aplurality of physical devices 142. By virtue of such arrangement, evenwhen a plurality of processing requests are issued to one and the samelogical device 143, these processing requests can be processed,respectively, by the relevant physical devices 142 in parallel, so longas the extents of the plural input/output processing requests aredestined for the physical devices which differ from one another. Thus,the processing efficiency can be enhanced.

FIG. 2 is a view for illustrating a heading or leading portion of a CCWchain (Channel Command Word chain) with which channel requests forreading data as an example of the instruction or commands and datagroups transferred between the host processor 10 and the control unit 12by way of the channel 11. Referring to FIG. 2, a command “Define Extent”serves for defining the range or extent of the input/output processingof a succeeding command, a cache access mode and the like. A command“Locate Record” validates or enables seek and search operations for atarget or object record, while a command “Read Data” designates readoperation of the relevant data. The extent information designated by thecommand “Define Extent” has heretofore been used for rejecting theexecution in case the succeeding input/output command is out of therange or extent. By contrast, according to the teachings of the presentinvention, the extent information is stored in the control memory 124for the exclusive control, which will be described later on.

(B) Logical Device Control Information Stored in Control Memory ofControl Unit

FIG. 3 is a view for illustrating logical device control tables 30stored in the control memories 124 incorporated in the control unit 12in the system according to the present invention. The number of thelogical device control tables 30 as provided may be equal to that of thelogical devices 143 controlled by the control unit 12, wherein each ofthe logical device control tables is affixed with a logical device IDnumber 301 as the identifier for identifying the relevant logicaldevice.

Upon issuance of an input/output processing request from a given one ofthe host processors 10, an input/output processing managing area 302 isallocated to the logical device control table relevant to theinput/output processing as requested. For identifying the input/outputprocessing, relevant one of the input/output processings is assignedwith the input/output processing control table ID number 303 which isthen stored in the input/output processing managing area 302.Additionally, for identifying discriminatively the host processor whichexecuted the input/output processing, there is stored in the relevantlogical device control table (30) a path group identifier or identifiers304 prescribed by the relevant host processor 10 for one or plural pathsets intervening between the individual host processors 10 and thecontrol unit.

(C) Input/Output Processing Control Information Stored in Control Memoryof Control Unit

FIG. 4 is a view showing input/output processing control tables 40designed for storing individual information of the input/outputprocessings, respectively, which are requested for the control unit 12.Each of the input/output processing control tables 40 is affixed withthe input/output processing control table ID number 303 as an identifierfor identifying the input/output processing. The input/output processingcontrol table ID number corresponds to the input/output processingcontrol table ID number 303 shown in FIG. 2. Stored in each of theinput/output processing control tables 40 is the extent information 401which is based on the command “Define Extent” sent from the hostprocessor 10.

The extent information 401 contains a start address and an end addressof the relevant logical device determined on the basis of the extent ofthe input/output processing request designated by the command “DefineExtent”, to thereby define the extent of the logical device over whichthe input/output processing is to be performed. The control unit of thestorage system according to the present invention is so designed orprogrammed as to perform the exclusive control on the basis of theextent information 401. Consequently, when the extent information 401 ofa given input/output processing overlaps with that of the otherinput/output processing which is being currently executed, the giveninput/output processing is forced to wait for the start of executionthereof, which is referred to as occurrence of wait event. In this case,information concerning the relevant wait-event occurrence time 402 isstored in the input/output processing control table.

Further, upon execution of the input/output processing requested by thehost processor 10, decision is made as to whether this processing isactivated initially or it has been forced to wait for execution by theexclusive control and is executed by restarting. To this end, there isprovided the reconnection-relating information 403 in which informationindicating the reconnection is set when execution of an input/outputprocessing is to be restarted from the waiting state.

(D) Path Group Identifier Information Stored in Control Memory ofControl Unit

FIG. 5 is a view illustrating a structure of the path group identifiertable 50 for acquiring the path group identifier to thereby determine inwhich of the host processors the input/output processing request issuedto the control unit originates. The path group identifier table 50 isresident in the control memory 124 incorporated in the control unit.More specifically, a number of areas equal to that of the paths whichinterconnect the control unit and the host processors are provided onthe control memory 124, wherein one path group identifier 304 candefinitely be identified by one path identifier 501. To say in anotherway, one-to-one correspondences are established between the pathidentifiers and the path group identifiers, respectively.

(E) Extent-Based Exclusive-Use Suppression Control Information Stored inControl Memory of Control Unit

FIG. 6 is a view for illustrating a structure of the extent-basedexclusive-use bypass or suppression control table 60 which table isreferred to when the exclusive control is to be suppressed or bypassedon a logical-device basis due to the extent designated by the serviceequipment 13 or by the command of the host processor. The extent-basedexclusive-use suppression control tables 60 are prepared in a numberequal to that of the logical device ID numbers 301. When theextent-based exclusive use is to be suppressed, information indicatingthe suppression is set in the relevant extent-based exclusive-usesuppression control information 601.

(F) Extent-Based Exclusive Control Operation

FIGS. 7 to 9 are flow charts for illustrating the exclusive controlperformed on an extent-by-extent basis upon reception of commands forplural input/output processings for one volume from plural hostprocessors by the host adaptors 122.

More specifically, FIG. 7 is a flow chart for illustrating a processingprocedure executed when a command for input/output processing isreceived by the host adaptor 122 from the host processor.

If an extent exclusive control is not suppressed by a service equipmentor a host, upon issuance of the input/output processing request from agiven one of the host processors, decision is made in a step 702 as towhether or not the extent-based exclusive-use suppression controlinformation 601 indicating that the exclusive control taught by thepresent invention is to be evaded or suppressed for the logical deviceto which the input/output processing request mentioned above is directedhas been set in the extent-based exclusive-use suppression control table60 stored in the control memory 124 of the control unit by the externalservice equipment or by other host processor. When bypassing oravoidance of the exclusive control is set, the processing proceeds to astep 703, whereupon the exclusive control is performed on alogical-device basis as in the case of the conventional techniquesdescribed hereinbefore, for thereby allowing the input/output processingas requested to be executed continuously (step 706). On the other hand,unless the bypassing or avoidance of the exclusive control is set, theprocessing proceeds to a step 704. In this step 704, it is decidedwhether the input/output processing request mentioned above is validatedby the reconnection or activated initially. The above decision can bemade on the basis of the reconnection-relating information 403 containedin the input/output processing control table 40 which is stored in thecontrol memory 124 of the control unit. In case the input/outputprocessing request is activated by the reconnection, the processingproceeds to a step 706 to continue execution of the input/outputprocessing.

On the other hand, when the input/output processing request is the oneactivated initially, the logical device control table 30 is locked in astep 705, which is then followed by a step 707 where the relevant pathgroup identifier is acquired by referring to the path group identifiertable 50 with the path identifier of the activating path. In succession,in a step 708, the input/output processing managing area 302 of thelogical device control table 30 for the relevant logical device in whichthe path group identifier 304 is not registered is searched to therebysecure the input/output processing managing area 302 in which the pathgroup identifier has not yet been registered. In a step 709, the pathgroup identifier 304 and the input/output processing control table IDnumber 303 capable of identifying the input/output processing arerecorded to be used as the information for making decision as to whichof the host processors the input/output processing request now concernedoriginates in.

FIG. 8 is a flow chart for illustrating a processing procedure forexecuting the extent-based exclusive control by storing the informationconcerning the extent (i.e., extent information) of the input/outputprocessing request received from a host processor in the input/outputprocessing control table 40 prepared on the control memory 124 and bymaking decision as to the overlap of the extent with that of otherinput/output processing. Referring to the figure, decision is made in astep 801 as to whether or not the input/output processing requesttransferred from the host processor contains information concerning theextent (extent information). When the extent information is transferred,the transferred extent information is recorded as the extent information401 of the relevant input/output processing control table ID number 303stored in the logical device control table 30 (step 802). On the otherhand, when no extent information is available, the start address and theend address of the relevant logical device are recorded as the extentinformation 401, whereupon the exclusive control is executed with thewhole volume being regarded as one extent (step 803).

Subsequently, in a step 804, decision is made for the relevant logicaldevice whether or not the extent information 401 of the input/outputprocessing to be executed overlaps with the extent information 401 forthe other input/output processing request. When overlap is found,information of the wait-event occurrence time 402 is recorded in theinput/output processing control table 40 for the processing which isforced to wait for (step 805), whereon the logical device control table30 is released from the locked state in a step 806. Unless overlap isfound, the logical device control table 30 is immediately unlocked inthe step 806.

When the overlap is determined in a step 807, the reconnection-relatinginformation 403 is set in the input/output processing control table 40in a step 808, whereon interconnection with the host processor iscleared in a step 809. Then, the extent-release awaiting state isvalidated until the reconnection request is issued with the relevantextent being released (step 810). By contrast, when no overlap isdecided in the step 807, the input/output processing is executed in astep 811.

In case the input/output processing command is a read data command,then, data is read out from the cache memory when the data which oversthe range of the input/output processing request is resident on thecache memory. By contrast, unless the data covering the range or extentof the input/output processing request is available from the cachememory, the data is read out from the array-type external storage unit14. Upon completion of the input/output processing (read processing inthis case), the procedure proceeds to the input/output terminationprocessing. By virtue of the exclusive control based on the extentinformation according to the present invention, a plurality ofinput/output processings can be executed for one and the same logicaldevice so long as no overlap occurs in respect to the extent. Further,when these plural input/output processings are to be executed for themutually different logical devices and when relevant data is unavailablefrom the cache memory (cache miss event) the data reading from theplural physical devices of the array-type external storage can beexecuted in parallel. However, when the physical devices are being usedfor executing the input/output processing for the same logical device orfor the other logical device, the device-busy state is set.

In case the input/output processing command is a write command, datacovered by the range or extent of the input/output processing request iswritten in the cache memory. Thereafter, the data is written in thelogical device by the control unit, being transferred from the cachememory. Upon completion of the input/output processing, the procedureproceeds to the input/output termination processing.

FIG. 9 is a flow chart for illustrating the processings involved whenthe input/output processing procedure is terminated through the hostadaptor 122. In a step 901, the logical device control table 30 islocked, which is then followed by a step 902 where the path groupidentifier 304 set in the relevant input/output processing managing area302 is deleted for thereby allowing the relevant extent to be released.

In a step 903, for the logical device for which the input/outputprocessing is to be terminated, decision is made as to presence of theinput/output processing which is in the waiting state because of overlapof the extent with that of the input/output processing to be terminatedthrough comparison with the extent information 401 placed in theinput/output processing control table 40 corresponding to the otherinput/output managing area for the logical device mentioned above and bychecking whether or not the wait-event occurrence time 402 is stored.Unless the wait-event occurrence time 402 is recorded in theinput/output processing control table 40 or unless overlap of the extentoccurs even when the wait-event occurrence time is recorded, the logicaldevice control table 30 is released from the locked state in a step 906,whereupon the processing procedure comes to an end.

In case the wait-event occurrence time 402 is stored and when theinput/output processing control table 40 for which the extent overlapwith the input/output processing to be terminated exists, one of theinput/output processing control tables in which the wait-eventoccurrence time 402 is oldest is selected in a step 904 for allowing theinput/output processing managing area 302 of the selected input/outputprocessing control table 40 to be made active. In a step 905, the hostprocessor to be reconnected is specified on the basis of the path groupidentifier 304 placed in the corresponding input/output processingmanaging area 302 corresponding to the selected input/output processingcontrol table 40, whereupon request for reconnection is issued to thespecified host processor while the logical device control table 30 isreleased from the locked state in a step 906. Subsequently, theinput/output processing activated through the reconnection is executedin succussion.

(G) Avoidance of Extent Exclusive Control

When avoidance of the exclusive control on the extent-by-extent basisdescribed previously is commanded by the service equipment having thefunction for performing input/output operation on the control memory 124of the control unit or designated by the control information sent to thecontrol unit from the host processor, the extent-based exclusive controlis not carried out for the logical volumes designated by the command. Inthat case, the input/output processing is performed in accordance withthe conventional logic.

As will now be appreciated from the foregoing description, in thestorage system according to the present invention, exclusive control forplural input/output processing requests issued for one logical devicefrom the host processors is performed on the basis of the range orextent of the input/output processing requests. By virtue of thisfeature, when the relevant data exists on the cache memory of thecontrol unit and thus the access to the physical device is unnecessaryor when access is made to the data on one and the same logical deviceset up over the different physical devices of the array-type externalstorage unit, efficiency of data input/output operation can be enhancedsurprisingly, whereby throughput of the system as a whole can beimproved significantly.

1. An array system comprising: a plurality of disk drives; and a controlunit for controlling read/write of data requested by a plurality of hostprocessors into the plurality of disk drives, using a plurality oflogical volumes constituted by storage areas of the plurality of diskdrives, and the control unit being controllable to allow or delay a readrequest or a write request sent from a host computer which has noexclusive control function, by controlling allowance or delay of theread request or the write request based on information received from thehost computer with the read request or the write request, wherein, whenthe control unit receives multiple requests from different hostprocessors for a logical storage area having a different size than asize of one of the logical volumes, the control unit controls to allow afirst read request or write request of the multiple requests andcontrols to delay a second read request or write request of the multiplerequests, and wherein, if the information received by the control unitfrom the host processor includes information as to the logical storagearea, the control unit controls allowance or delay of the read requestor the write request by using the logical storage area, but if theinformation received from the host processor does not include theinformation as to the logical storage area, the control unit controlsallowance or delay of the read request or the write request by using thelogical volumes.
 2. The system according to claim 1, wherein the controlunit includes a plurality of host adaptors which control data transferbetween the control unit and the plurality of disk drives.
 3. The systemaccording to claim 2, wherein the control unit includes a plurality ofdisk adaptors which control the read/write of data from/to the pluralityof logical volumes.
 4. The system according to claim 3, wherein thecontrol unit includes cache memories which enable the transfer of databetween the host adaptors and the disk adaptors.
 5. The system accordingto claim 1, wherein the control unit includes a plurality of diskadaptors which control the read/write of data from/to the plurality oflogical volumes.
 6. The system according to claim 1, wherein the controlunit includes a control memory which stores control information into aplurality of tables.
 7. The system according to claim 1, wherein thecontrol unit controls to delay the second read or write request of themultiple requests if a data range of the second read or write requestand a data range of the first read or write request overlap a samelogical storage area and the control unit permits the second read orwrite request and the first read or write request to be handled inparallel if their data ranges do not overlap in the same logical storagearea.
 8. The system according to claim 1, wherein the logical storagearea is an extent corresponding to a portion of said one of the logicalvolumes.
 9. An array system comprising: a plurality of disk drives; anda control unit for controlling read/write of data requested by aplurality of host processors into the plurality of disk drives, using aplurality of logical volumes constituted by storage areas of theplurality of disk drives, the control unit being controllable to allowor delay a read request or a write request sent from a host computerwhich has no exclusive control function, by controlling allowance ordelay of the read request or the write request based on informationreceived from the host computer with the read request or the writerequest, wherein, when the control unit receives multiple requests fromdifferent host processors for a logical storage area having a differentsize than a size of one of the logical volumes and determines that thedata ranges of the multiple requests overlap, the multiple requests arenot handled in parallel, and wherein, if the information received by thecontrol unit from the host processor includes information as to thelogical storage area, the control unit controls allowance or delay ofthe read request or the write request by using the logical storage area,but if the information received from the host processor does not includethe information as to the logical storage area, the control unitcontrols allowance or delay of the read request or the write request byusing the logical volumes.
 10. The system according to claim 9, whereinthe control unit includes a plurality of host adaptors which controldata transfer between the control unit and the plurality of disk drives.11. The system according to claim 10, wherein the control unit includesa plurality of disk adaptors which control the read/write of datafrom/to the plurality of logical volumes.
 12. The system according toclaim 11, wherein the control unit includes cache memories which enablethe transfer of data between the host adaptors and the disk adaptors.13. The system according to claim 9, wherein the control unit includes aplurality of disk adaptors which control the read/write of data from/tothe plurality of logical volumes.
 14. The system according to claim 9,wherein the control unit includes a control memory which stores controlinformation into a plurality of tables.
 15. The system according toclaim 9, wherein the logical storage area is an extent corresponding toa portion of said one of the logical volumes.